What Size Generator for a CPAP Machine?
Any generator runs a CPAP; the machine itself draws 30 to 60 watts. The numbers that matter are the heated humidifier (add 150 to 250W when it's on) and the hours: a full night is 8 hours of continuous, silence-adjacent, clean power, which is why the honest first recommendation here is a battery power station, with the generator as its daytime charger.
Wattage by type
| CPAP machine type | Running | Starting |
|---|---|---|
| CPAP, humidifier off | 30 to 60 W | no surge |
| CPAP + heated humidifier | 150 to 250 W | no surge |
| CPAP + humidifier + heated hose | 200 to 300 W | no surge |
| BiPAP | 60 to 100 (add humidifier as above) W | no surge |
What it takes with company
Same engine as the wattage picker: running total plus the single biggest start spike, then the smallest class that carries it with 20% headroom.
| Load list | Running | Peak | Buy |
|---|---|---|---|
| CPAP + humidifier alone | 250 W | 250 W | 2,200W inverter |
| CPAP + humidifier + fridge + the basics | 1,150 W | 2,650 W | 3,400W inverter |
The details that change the answer
Run the watt-hours, not the watts. A CPAP with the humidifier off uses about 30 to 60W, so a night is under 500 watt-hours: comfortably inside a mid-size power station, silently, next to the bed, no carbon monoxide within a hundred feet of your airway. Turn the heated humidifier on and the draw quadruples, which halves-to-quarters the battery math; most machines have a non-heated passover mode for exactly this situation, and using it during outages is the single best trick on this page.
Where the generator earns its place is duration. Multi-day outage, the station runs the nights and the generator (already out there for the fridge) recharges it each morning; 500Wh of recharge is about 20 minutes of one refrigerator-scale load. If you'd rather run the CPAP on the generator directly, any inverter unit is enormously oversized for the job and does it fine; use the 12V or DC adapter kit your CPAP maker sells if you want to skip the wall-adapter conversion losses. Talk to your DME supplier about the manufacturer's official battery, too; insurance occasionally covers it.
Questions people ask
How long will a power station run a CPAP?
Divide the station’s watt-hours by your draw: a 500Wh station runs a 45W machine (humidifier off) about 9 to 10 hours after inverter losses, one full night. With a heated humidifier at 200W total it is 2 to 3 hours, which is why humidifier-off is the outage setting. A 1,000Wh station covers two nights dry or one humid night with margin.
Is generator power safe for a CPAP?
From an inverter generator or through a power station, yes; both produce cleaner power than a bad grid day. Cheap open-frame generators with high distortion are the ones to keep away from medical equipment, or buffer with a small UPS. And the machine is at your face all night, so the generator stays its full 20 feet from the house regardless of how nice its sine wave is.